This invention relates to an air conditioner with a radiant temperature control and, more particularly, to an air conditioner using a heat pump type refrigeration cycle.
In air conditioners with a heat pump type refrigeration cycle, a four-way valve, an outdoor heat exchanger, a pressure reducing unit, and an indoor heat exchanger are connected in series to a compressor. Some air conditioners of this type control a room's temperature using a radiant temperature from a wall or floor of the room (or air-conditioning space).
Conventionally, the input port of a control circuit used in such an air conditioner is connected to a room temperature sensor for detecting the room temperature and to a radiant temperature sensor for detecting the radiant temperature from a wall or floor of the room. The output port of the control circuit is connected to a compressor constituting a refrigeration cycle. The control circuit compares the room and radiant temperatures. As a difference between the two temperatures increases, the compressor output is increased; and as the difference decreases, the compressor output is decreased. Alternatively, a target temperature preset by a temperature setting means is corrected in accordance with the difference.
In this system, however, the radiant temperature varies less than the room temperature. Therefore, ideal air-conditioning cannot always be performed with the above system.
For example, when a defrosting cycle starts during a heating operation or someone opens a window in the room abruptly, the room temperature changes greatly and the person in the room perceives that it is cold due to the temperature change. However, the heat capacity of the wall or floor is large, and the radiant temperature varies less than the room temperature. Therefore, the control circuit erroneously determines that the room has a high relative radiant temperature and controls the compressor in accordance therewith. More specifically, when the temperature is stable, a difference between the room and radiant temperatures in a specific period of time defined as .DELTA.T1, at which a comfortable temperature is maintained. In the next period of time, if defrosting is started or someone opens a window abruptly, the room temperature is greatly changed, and the difference between the room and radiant temperatures is decreased to .DELTA.T2 (.DELTA.T1&gt;.DELTA.T2). The room temperature is thus decreasd, resulting in a low perceived temperature. However, it is determined that the apparent radiant temperature is increased, and the target temperature is decreased in accordance with this determination.
In addition, the above air conditioner performs temperature control in the same manner for both cooling and heating operations. However, since people wear different amounts of clothing in summer and winter, temperatures perceived in those two seasons are different, even when temperatures vary in the same range. An increase in room temperature of one degree is perceived as a greater temperature increase during the summer than it is during the winter. When target temperature is corrected to correspond to the radiant temperature in the same manner during both cooling and heating operations, the resultant perceived room temperatures are different, thereby disabling comfortable air conditioning. In other words, when the target temperature is increased by one degree during a cooling operation, users perceive the temperature to be higher than the actual temperature increase.